Piston



Aug. 23, 1932. G. E. FRANQUIST PISTON Original Filed May 26. 1922 2 Sheets-Sheet l Aug. 23, 1932. E. FRANQUIST PISTON Original Fiied May 26, 1922 2 Sheets-Sheet 2 Patented Aug. 23, 1932 UNITED STATES PATENT OFFICE GUSTAVE E. FRANQUIST, DECEASED, LATE OF ROCHESTER, NEW YORK, BY MARGARET LOUISE FRANQUIST, EXE-OUTRIX, OF ROCHESTER, NEW YORK, ASSIGNOR TO THE CLEVELAND TRUST COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO PISTON Original application filed May 26, 1922,

This invention relates to pistons for internal combustion, steam and other engines, and is a division of copending application Serial'No. 563,782 filed May 26, 1922, now Patent No. 1,826,171, granted October 6, 1931.

This inventionrelates generallyto any type of piston having a head and a skirt which are separated partially on a peripheral surface by a circumferential slot, groove, or other means of separation, and in which the skirt has one of its main cylinder-engaging portions formed with a longitudinal slot.

One of the objects of the present invention is to provide such a piston which will substantially eliminate piston slap at all speeds and temperatures of the engine in which it operates.

Another object is to provide such a piston of improved design which will closely fit the walls of the engine cylinder in which it operates without seizing with or scoring the cylinder walls at operating temperatures of the engine.

Another object is to provide such a piston with a longitudinally slotted skirt having a main working portion physically separated from the head by a circumferential slot, and

relieved areas about the piston pin bosses extending well beyond the terminations of the circumferential slot to insure against seizure of the skirt with the cylinderjwalls during expansion of the piston.

A further object is to provide a piston having opposite boss carrying portions integrally connected with the head and a longitudinally slotted cylinder-engaging portion between and joined with the boss car rying portions and physically separated from the head by a circumferential slot of greater circumferentiallength than the corresponding length of the cylinder-engaging portion, the boss carrying portions having a circumferential relief extending from their upper ends to points below the bosses and extending circumferentially beyond the terminations of the circumferential slot.

With the above and other objects in view, the present invention may be said to comprise the piston illustrated in the accom Serial No. 563,782. Divided and this application filed April 22,

Serial No. 531,962.

and set forth in the appended claims, together with such variations and modifications thereof as will be apparent to one skilled in the art to which the invention appertains.

Referring to the drawings, which illustrate a suitable embodiment of the present invention;

Figure 1 is a perspective view of a slotted skirt piston showing the relieved area in the vicinity of the wrist pin bosses thereof extending beyond the slot that separates one of the cylinder-engaging portions of the skirt from the head;

Fig. 2 is a perspective view of a piston similar to Fig. 1, wherein the relieved area gradually merges into the circumferential working faces of the skirt;

Fig. 3 is a perspective view similar to Fig. 1, in which the relieved area extends completely to the open end of the piston skirt;

Fig. 4 is a perspective view similar to Fig. 2, in which the relieved area extends entirely to the open end of the piston skirt.

Ithas been found in a piston having opposite cylinder-engaging portions, one of which is physically separated from the piston head, that if the piston skirt is properly relieved, the piston can be snugly fitted within the engine cylinder in such a manner as to eliminate piston slap at all operating speeds and temperatures of the engine, andat the same time insure against seizure of the piston against scoring of the cylinder walls or pis ton.

Relief, as applied to pistons, may be termed an external peripheral undercutting of portions of the piston skirt, so that such re lieved portions will not come into contact with the cylinder walls during operation of the piston. I

In a piston havinga main cylinder-engaging portion physically separated from the head by 'a circumferential slot, all portions of the skirt, with the exception of the portion that is physically separated from the head, tend to move radially outwardly from the upper or head end of the skirt in decreasing measure to the open' end, during radial .ex-

pansion of the head incident to heating thereof. In a piston 'of the character mentioned, this is the case with the skirt portion lying between the portions intercepted by the chord of the are that represents the extent of the circumferential separating slot.

The vreliefs contemplated by the present invention should, because of the rigidity of the piston structure in general, extend circumferentially over the wrist pin boss supporting portions that are integral with the head, and

well beyond the same, that is, well over onto that is separated from the head, since in this case the expansion of the boss carrying portions, due to the heat conducted thereto from the head, will tend to carry the longitudinal side portions in the independently functioning, cylinder-engaging part at the extremities of the boss carrying portions into the cylinder wall, resultingin either increased frictional losses, or the necessity of fitting the piston skirt within the cylinder with greater clearances. This is an undesirable condition and is one which the piston of the present invention will, overcome.

The opposite reliefs may longitudinally extend the entire length of the piston skirt or to a region below the bosses, as desired. It

is important,-however, that the piston skirt 1 adjacent the bosses should be well relieved in those portionsimmediately adjacent to the.

head.

It has'been found that, by relieving a piston of the character specified in the manner contemplated by the present invention, the piston can be fitted within the cylinder with considerably less clearance than is possible where the boss-carrying portion reliefs do not extend beyond the ends of the separating slot.

Referring to the accompanying drawings,-'

in which like numerals refer to like parts throughout the several views, the piston to which the present invention relates comprises a head 1 and a skirt 2. The skirt 2 embodies 4 rigid opposite portions A which carry the shown in head by the circumferential slot 4.

It will be noted from the drawings that the relief 6 extends circumferentially over the boss carrying portion A and into the peripheral surface of the independently func tioning cylinder-engaging portion B, well beyond the termination of the circumferential slot 4, thus making the circumferential length of the independently functioning cylinderengaging portion of lesser extent than the corresponding length of the circumferential separating slot 4.

The portions A of the piston skirt 2 ad jacent the wrist pin bosses, which are physically integral with the piston' head 1, are subject to the mechanical expansion produced by the thermal expansion of the head 1. This expansion acts radially in all directions, and because of the rigidity of the boss carrying portions, causes all portions of the skirt, with the exception of the independently functioning portion B underlying the circumferential slot 4, to move mechanically outwardly. These portions, however, will also be moved outwardly for some little distance past the points where the boss carrying portions are actually-cut byvthe circumferential slot 4.

In actual practice, the length of the chord subtending the circumferential slot will vary, but in all cases, the reliefs 6 should extend well beyond the terminations of the slot 4.

It is not the purpose of the present invention to confine thereliefs 6 to any particular type. They may be of reduced diameter, as

igures 1 and 3, or they may be of a maximum depth adjacent and opposite the wrist pin bosses and gradually decrease to nothing and merge into the independently functioning cylinder-engaging portion at the proper point beyond the portions cut by the circumferential slot. I Furthermore, the reliefs may longitudinally extend from the upper end of the skirt to the regions below the bosses, as shown in Figures 1 and 2, or as shown in Figures 3 I the piston skirt.

It is to be partlcularly noted that one of the main cylinder-engaging portions of the present invention is physically separated from the head by a circumferential slot and is slotted longitudinally and, futhermore, that the. skirt is relieved in such a manner that, in the completed piston, the circumferential separating slot is of greater circumferential length than the corresponding length of the actual bearing face of the cylintier-engaging portion underlying the circumferential slot.

It is clearly apparent'to those skilled in the art that the present invention provides a new and improved piston which will operate more efficiently at all speeds and operating temperatures'of the engine, and which will substantially prevent piston slap at all operating temperatures and speeds.

It is also apparent that a relatively snug fit may be maintained between the engine cylinder and the cylinder-engaging portions of the piston-skirt of the present invention, at all operating temperatures,'and that the piston skirt, in spite of the snug fit or small clearance, will not stick or seize with the cylinder during the expansion of the piston head.

Furthermore, it is to be understood that the particular forms of apparatus shown and described, and the particular procedure set forth are presented for purposes of explanation and illustration and that various modifications of said apparatus and procedure can be made without departing from this invention as defined in the appended claims.

What is claimed is:

1. A piston comprising a head and a skirt integrally united with said head, said skirt comprising opposite circumferential boss carrying portions each having an inwardly extending wrist pin boss thereon, and opposite cylinder-engaging portions arranged between and integral with said boss carrying portions, one of said cylinder-engaging portionsbeing physically separated from said head by a circumferential slot and being slotted longitudinally through the thickness of its wall, said skirt in the region adjacent said head being externally and circumferentially relieved over said boss carrying portions and beyond the terminations of said circumferential slot;

2. A one piece piston comprising a head and a skirt, said skirt embodying opposite cylinder-engaging portions, opposite boss carrying portions integral with said head and integral with said cylinder-engaging portions, and wrist pin bosses carried by sai boss-carrying portions, one of said cylinderengaging portions being physically separated from said head by a circumferential slot and being slotted longitudinally between the longitudinal side edges thereof, said skirt at each of the boss-carrying sides thereof having a circumferentialrelief overrthe bosses and adjacent the head, which is of maximum depth over the bosses and which gradually decreases in depth and merges into the peripheral face of the longitudinally split cylinder-engaging portion well beyond the termination of said circumferential slot at that side of said skirt.

ferential boss carrying portions integral with said head and integral with said cylinder-engaging portions, and wrist pin bosses carried by said boss-carrying portions, one of said cylinder-engaging portions being physically separated from said head by a circumferential slot and being-slotted longitudinally between v the longitudinal side edges thereof, said skirt at each of the boss carrying sides thereof having a relief extending continuously and longitudinally from said head to a region below the adjacent boss and extending circumferentially to a region well beyond the termination of said circumferential slot at that side of said skirt.

4. A one piece piston comprising a head and a skirt, said skirt embodying opposite cylinder-engaging portions, opposite circumferential boss carrying portions integral with said head and integral with said cylinder-engaging portions, and wrist pin bosses carried by said boss-carrying portions, one of said cylinder-engaging portions being physically separated from said head by a circumferential slot and being slotted longitudinally between the longitudinal side edges thereof, said skirt at each of the boss-carrying sides thereof having a relief extending continuously and longitudinally from said head over the bosscarrying portion to the open end of said skirt and extending circumferentially to a region well beyond the termination of said circum ferential-slot at that side of said skirt.

5. A one piece piston comprising a head and a skirt, said skirt embodying opposite cylinder-engaging portions, opposite circumferential boss-carrying portions integral with said head and integral with said cylinder-engaging portions, and wrist pin bosses carried by said boss-carrying portions, one of said cylinder-engaging portions being physically separated from said head by a circumferential slot of greater circumferential length than the corresponding length of the said portion adjacent. said head, and being longitudinally slotted between the longitudinal side edges thereof, said skirt having external areas of d relief extending circumferentially over said boss-carrying portions and extending longi- ,tudinally to regions below said bosses, said areas of relief overlapping the ends'of said circumferential slot and terminating at the longitudinal side edges of said longitudinally 3. A one piece piston comprising a head andfa skirt, said skirt embodying opposite f no 

